To examine the effects of baseline and incident diabetes on cognitive function, Peggy J.J. Spauwen, from Maastricht University in the Netherlands, and colleagues conducted cognitive testing on 1,290 individuals (40 years or older) participating in the Maastricht Aging Study. Testing was performed at baseline and at six and 12 years.

At baseline, 68 participants had type 2 diabetes, while 54 and 57 had incident diabetes at the six- and 12-year follow-up, respectively. Over the 12-year follow-up, the researchers identified significantly larger decline in information-processing speed, executive function, and delayed word recall among those with diabetes at baseline, compared with control subjects. There was no significant difference noted in the decline for immediate word recall. Participants with incident diabetes showed subtle early decrease in information-processing speed only, compared to the controls; however, in other cognitive domains there was no larger decline observed.

"It seems that disease-exposure time plays an important role in the development of cognitive decline. This might provide a window of opportunity for prevention and early treatment of diabetes-related cognitive deficits," the authors write. "For this, it is important to assess cognitive status at an early stage of the disease and on a regular basis."